4. (8.21) A water solution needs to be heated from 25 to 85∘C as it moves at 0.25 m/s through a straight thin-walled sta

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4 8 21 A Water Solution Needs To Be Heated From 25 To 85 C As It Moves At 0 25 M S Through A Straight Thin Walled Sta 1 (71.3 KiB) Viewed 28 times

4. (8.21) A water solution needs to be heated from 25 to 85∘C as it moves at 0.25 m/s through a straight thin-walled stainless steel tube of 15−mm diameter. A uniform heat flux is maintained by an electric resistance heater wrapped around the outer surface of the tube. The solution properties are density =1000 kg/m3, specific heat=4000 J/kg K, kinematic viscosity =2×10−3 kg/sm, thermal conductivity =0.8 W/mK,Pr=10. a) If the tube is 12 m long, what is the required heat flux to achieve such temperature change? b) If the fluid enters the tube with a fully developed velocity profile and a uniform temperature profile, what is the surface temperature at the tube exit, and at a distance of 1.0 m from the entrance?